http://bugs.php.net/bug.php?id=31341

PHP fixed escaping of curly brackets in 5.1. You can't escape { anymore. (#1366982)

functions/imap_general.php

@@ -1079,7 +1079,7 @@ function sqimap_status_messages ($imap_stream, $mailbox,
  * @param $length
  */
 function sqimap_append ($imap_stream, $sent_folder, $length) {
-    fputs ($imap_stream, sqimap_session_id() . ' APPEND ' . sqimap_encode_mailbox_name($sent_folder) . " (\\Seen) \{$length}\r\n");
+    fputs ($imap_stream, sqimap_session_id() . ' APPEND ' . sqimap_encode_mailbox_name($sent_folder) . " (\\Seen) {".$length."}\r\n");
     $tmp = fgets ($imap_stream, 1024);
     sqimap_append_checkresponse($tmp, $sent_folder);
 }